Process for preparing stable dispersions of starch particles

ABSTRACT

In one or more embodiments, the present disclosure provides for a process for preparing a dispersion of starch particles in an aqueous liquid. In one or more embodiments, the process includes introducing a feed starch and the aqueous liquid into a rotor stator mixer, maintaining the feed starch and the aqueous liquid in the rotor stator mixer at a temperature ranging from a gelation temperature to less than a solubilization temperature, and shearing the feed starch into starch particles with the rotor stator mixer to form the dispersion of starch particles in the aqueous liquid. In one or more embodiments, the starch particles produced by this process have an average particle size diameter of no larger than 2 micrometers and the dispersion has 20 to 65 weight percent of the starch particles based on a total weight of the dispersion.

This application is a Continuation of U.S. application Ser. No.13/153,854, filed Jun. 6, 2011, which claims the benefit to U.S.Provisional Application Ser. No. 61/352,209, filed Jun. 7, 2010, theentire contents of which are incorporated herein by reference in itsentirety.

FIELD OF DISCLOSURE

Embodiments of the present disclosure are directed toward a process forpreparing starch; more specifically, embodiments are directed toward aprocess for preparing stable dispersions of starch particles.

BACKGROUND

Synthetic latexes are important components in the binder systems ofcoatings used in the paper coating industry. Synthetic latexes used inthese applications typically have a high solid content (48-58 weightpercent solid) and a low viscosity that allows for ease of handling, andgood runnability and stability in the paper coating process. Syntheticlatexes also allow for excellent particle size control, viscoelasticitycontrol (e.g., glass transition temperature (Tg) and modulus), and dryand wet strength of the resulting coatings.

In addition to synthetic latexes, starch can also be useful in thebinder systems of coatings used in the paper coating industry. Forexamples, starch has been used as a partial substitute for syntheticlatexes in the binder systems of coatings used in the paper coatingindustry. Among its advantages, starch is a relatively low cost materialhaving excellent water holding and thickening properties while providingstiffness, porosity and blocking resistance to the resulting coating.There are, however, limitations in the use of starch in theseapplications. These limitations include poor runnability duringapplication and poor product performance of the coating compositions,especially as the level of latex substitution increases.

To overcome these challenges, it would be advantageous for paper coatingapplications, among others, to develop a starch product which can bemade at a high solid content (45-65 weight percent) while maintaining alow viscosity of 2000 cP or less similar to synthetic latexes, andpreferably with an average particle size diameter of no larger than 2micrometers.

SUMMARY

One or more embodiments of the present disclosure include a process forpreparing a stable dispersion of starch particles in an aqueous liquid.In one or more embodiments, the process includes introducing a feedstarch and the aqueous liquid into a rotor stator mixer, maintaining thefeed starch and the aqueous liquid in the rotor stator mixer at atemperature ranging from a gelation temperature to less than asolubilization temperature of the feed starch, and shearing the feedstarch into starch particles with the rotor stator mixer to form thestable dispersion of starch particles in the aqueous liquid.

In one or more embodiments, shearing the feed starch into starchparticles produces starch particles having an average particle sizediameter of no larger than 2 micrometers. Other average particle sizediameters for the starch particles are also possible. For example, inone or more embodiments shearing the feed starch into starch particlesproduces starch particles having an average particle size diameter of nolarger than 1 micrometer. In another example, in one or more embodimentsshearing the feed starch into starch particles produces starch particleshaving an average particle size diameter of 10 to 200 nanometers.

In one or more embodiments, shearing the feed starch into starchparticles includes forming the dispersion having 20 to 65 weight percentof the starch particles based on a total weight of the dispersion. Inone or more embodiments, shearing the feed starch into starch particlesincludes forming the dispersion having 35 to 55 weight percent of thestarch particles based on a total weight of the dispersion. In one ormore embodiments, shearing the feed starch into starch particlesincludes forming the dispersion having 45 to 55 weight percent of thestarch particles based on a total weight of the dispersion. In one ormore embodiments, shearing the feed starch into starch particlesincludes forming the dispersion having 48 to 55 weight percent of thestarch particles based on a total weight of the dispersion.

In one or more embodiments, the starch particles are sheared in theabsence of a cross-linker. In one or more embodiments, shearing the feedstarch into starch particles is conducted in the absence of a surfactantand/or a cross-linker. In one or more embodiments, shearing the feedstarch into starch particles is conducted in the presence of asurfactant and/or a cross-linker. In one or more embodiments, shearingthe feed starch, in addition to producing starch particles, producessoluble starch having a starting molecular weight, where the solublestarch can be reduced from the starting molecular weight to an endingmolecular weight that is less than the starting molecular weight. In oneor more embodiments, reducing the soluble starch includes enzymaticallyreducing the soluble starch from the starting molecular weight to anending molecular weight less than the starting molecular weight.

In one or more embodiments, the viscosity of the dispersion having 20 to65 weight percent by weight of the starch particles, based on a totalweight of the dispersion, is less than 10,000 cP after being at 25° C.for at least 24 hours, for example at 24 hours. In one or moreembodiments, the process of the present disclosure also includes atleast partially removing the aqueous liquid from the starch particles ofthe dispersion.

In one or more embodiments, the dispersion of starch particles preparedby the process of the present disclosure can be included in a bindercomposition, an adhesive composition and/or a coating composition. Inone or more embodiments, the coating composition can be a paper coatingcomposition, among other types of coating compositions. In one or moreembodiments, the coating composition can be a filth forming composition.In one or more embodiments, the coating composition can be applied toone or more surfaces of a substrate. In one or more embodiments, thecoating composition applied to one or more surfaces of the substrate canhave at least a portion of the aqueous liquid removed, thereby forming acoating layer (e.g. a film), a binder layer or an adhesive layerassociated with one or more surfaces of the substrate. In one or moreembodiments, the coating layer, binder layer or the adhesive layerformed with the dispersion produced according to the present disclosurecan be continuous, discontinuous, or combinations thereof. In one ormore embodiments, removing at least a portion of the aqueous liquid canbe removed via drying, centrifuge, freeze drying, filtration, absorptionand combinations thereof. In one or more embodiments, an article can beformed with the coating composition, where the article can have asubstrate having one or more surfaces, and one or more coating layersassociated with one or more surfaces of the substrate, where the coatinglayer is derived from the coating composition.

The above summary of the present disclosure is not intended to describeeach disclosed embodiment or every implementation of the presentdisclosure. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a transmission electron microscopy (TEM) image of asoluble starch from a feed starch that has been “cooked” beyond thesolubilization temperature but not gelled according to the presentdisclosure.

FIG. 2 provides a TEM image of a stable dispersion of starch particlesin an aqueous liquid according to the present disclosure.

FIG. 3 provides an optical microscope image of starch granules formedfrom a feed starch in an aqueous liquid but kept below the geltemperature during shearing.

DEFINITIONS

As used herein, the terms “a,” “an,” “the,” “one or more,” and “at leastone” are used interchangeably and include plural referents unless thecontext clearly dictates otherwise.

Unless defined otherwise, all scientific and technical terms areunderstood to have the same meaning as commonly used in the art to whichthey pertain. For the purpose of the present disclosure, additionalspecific terms are defined throughout.

As used herein, “μm” is an abbreviation for micrometer.

As used herein, “° C.” is an abbreviation for degree Celsius.

As used herein, “cP” is an abbreviation for Centipoise, a unit ofmeasurement in the cgs system for viscosity.

The terms “comprises,” “includes” and variations of these words do nothave a limiting meaning where these terms appear in the description andclaims. Thus, for example, a process that comprises “a” feed starch canbe interpreted to mean a process that includes “one or more” feedstarches. In addition, the term “comprising,” which is synonymous with“including” or “containing,” is inclusive, open-ended, and does notexclude additional unrecited elements or method steps.

As used herein, the term “and/or” means one, more than one, or all ofthe listed elements.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.).

As used herein, the term “feed starch” can include, a carbohydratepolymer composed of various ratios of amylose and amylopectin joined byglucosidic bonds and having and/or being in a crystalline orsemi-crystalline state. The feed starch can be selected from a widevariety of sources including, but are not limited to, corn, potato,tapioca, rice, wheat, barley, and other grains and/or tubers (e.g., rootor stem tubers), and of those may include waxy, native, unmodifiednative, and/or high amylose starches. Specific non-limiting examplesinclude waxy corn starch (e.g., a high amylopectin starch) and dentstarch, among others. The feed starch can also include “modified” feedstarch which can include a modified starch (e.g., corn, potato, tapioca,among others) prepared by acetylation, chlorination, acid hydrolysis,enzymatic action, or other modification process. This “modified” feedstarch can be purposefully modified in order to deliver other benefitssuch as carboxylated starches, hydroxyethylated starches, resistantstarches, thermally oxidized starches, dextrin type, among others. Inone or more embodiments, the feed starch can have a number of differentproperties and/or forms. These include, but are not limited to, a drypowder and/or an intermediate starch product such as a cake, and/or aslurry having moisture content in the range of equal or less than 80weight percent, for example, in the range of from 35 to 80 weightpercent; or in the alternative from 35 to 75 weight percent; or in thealternative from 35 to 65 weight percent. In one or more embodiments,the feed starch has discrete units having an average particle sizediameter of about 15 to about 40 micrometer (μm); for example, from 15to 35 μm; or in the alternative, from 15 to 30 μm; or in the alternativefrom 20 to 40 μm. Mixtures of two or more of the feed starch providedherein are also possible, and would be considered to be a “feed starch”as provided and discussed herein.

As used herein “dry” means no greater than about 8 to about 14 percentwater by weight absorbed in and/or bound to a substance (e.g., the feedstarch).

As used herein, the term “cross-linker” means a compound which attachesat least two chains of polymer molecules through carbon atoms by primarychemical bonds. In one or more embodiments, different categories of across-linker include, but are not limited to, Amino Resins (UreaFormaldehyde and Melamine Formaldehyde), Glyoxal Resins, and MetallicIons (Zirconium complexes). If a cross-linker is employed with thedispersion of the present disclosure, the selection of the cross-linkercan depend at least in part on the reactive groups available on thestarch particles, the ingredients of the coating, binder and/or adhesivecomposition and/or the end use of the coated substrate. The terminsolubilizer is also often used to define the function of crosslinkingchemistry in conjunction with starch.

As used herein, the term “surfactant” means a compound that reducessurface tension when dissolved in water or water solutions, or thatreduces interfacial tension between two liquids, or between a liquid anda solid.

As used herein, the term “soluble starch” means a starch released and/orleached from the feed starch granule into the aqueous liquid while beingheated to or at a temperature ranging from a gelation temperature tobelow a solubilization temperature of the feed starch, where the solublestarch is present in the aqueous phase between the starch particles ofthe present disclosure. In one embodiment, the soluble starch may beadditionally characterized by being small enough so as not to scatterlight in the visible spectrum (e.g., from about 380 or 400 nanometers toabout 760 or 780 nanometers). FIG. 1 provides a transmission electronmicroscopy (TEM) image of soluble starch forming a network of starchmolecules (e.g., the interconnected “spider web” like threads) withoutthe presence of the starch particles of the present disclosure, whichare shown in FIG. 2, as discussed herein.

As used herein, the term “dispersion” means a two-phase system where onephase consists of starch particles, as defined herein, dispersedthroughout an aqueous liquid, as defined herein, which forms acontinuous phase. For the present disclosure, starch particles can bedispersed in an aqueous liquid where the starch particles have anaverage particle size diameter of no larger than 2 micrometers.

As used herein, the term “aqueous liquid” includes water or a watersolution that can include compounds (ionic or non-ionic) such as organiccompounds, inorganic compounds, water soluble polymer, fats, oils,proteins, polysaccharides, salts, sugars, acids, alcohols, alkalis andgases that help to adjust and/or maintain a pH, a salinity, anelectrical conductivity, dielectric constant, and/or a boiling point,among others.

As used herein, the term “starch particles” refers to a discrete unitderived from the feed starch using the methodology of the presentdisclosure, where the discrete units have an amorphous structure and anaverage particle size diameter of no larger than 2 micrometers, whereaverage particle size diameters of no larger than 1 micrometers oraverage particle size diameters of 10 to 200 nanometers are possible.FIG. 2 provides a TEM image of a stable dispersion of starch particlesin an aqueous liquid according to the present disclosure, as is morefully discussed herein. The size and shape of the starch particles inFIG. 2 are in contrast to the optical microscope image of dispersedstarch granules shown in FIG. 3, where the starch granules were formedby shearing a feed starch in a rotor stator mixer at a temperature belowthe gelation temperature of the feed starch.

As used herein, the term “stable” or “stability” means the ability andthe duration of the starch particles of the present disclosure to remainas a dispersion in the aqueous liquid due to Brownian movement of thestarch particles in the aqueous liquid, where any settling of the starchparticles can be reversed by agitation. The stable dispersion of thestarch particles of the present disclosure does not gel or “set-up”under the conditions of the dispersion given herein.

As used herein, the term “rotor stator mixer” refers to a high-shearmixing apparatus that disperses, or transports, the starch particlesinto the aqueous liquid, as provided herein, by mechanical agitation. Inone or more embodiments, the rotor stator mixer includes at least oneimpeller or rotor, or a series of impellers and/or rotors, powered by amotor, e.g. an electric motor, and at least one stationary component(e.g., a stator) that creates a close clearance gap with the rotor so asto produce an extremely high shear zone for the material (e.g., the feedstarch) as it exits the rotor. Factors such as the diameter of the rotorand its rotational speed (e.g. ramps and cycles), the design of thestator ring such as number and rows of teeth, their angle and thedistance between the rotor and the stator (e.g., the clearance gap), theresidence time and the number of rotor stator mixers used all effect thegeneration of the dispersion of the starch particles in the aqueousliquid. Examples of such high-shear mixing apparatus include, but arenot limited to, batch high shear mixers, inline high shear mixers, ultrahigh shear inline mixers, and grinding mills. In one embodiment,embodiments of the rotor stator mixers, however, exclude extruders.

As used herein, the term “gelation temperature” refers to a temperatureand a pressure at which the crystalline structure of the feed starchtransforms at least partially from its crystalline and/orsemi-crystalline state to combine with the aqueous liquid to produce aviscous jellylike product.

As used herein, the term “solubilization temperature” refers to atemperature and a pressure at which the feed starch has no remainingcrystallinity and becomes a uniformly dispersed mixture at the molecularlevel in and with the aqueous liquid.

As used herein, the terms “swell,” “swelling,” and/or “swollen,” referto an increase in the volume of the feed starch due at least in part toa loss in crystallinity of the initial structure of the feed starch andthe absorption of an aqueous liquid into the resulting amorphousstructure of the feed starch.

As used herein, the term “ambient conditions” refers to a temperature ofaround 25° C. (e.g., 25° C.) and a pressure of 101.325 kiloPascal (kPa)(1 atmosphere).

As used herein, the term “specific mechanical energy (SME)” is definedas the total input of mechanical energy per unit mass of materialflowing through the rotor stator mixer of the present disclosure. Theunits of SME presented herein are in Joules per gram (J/g).

As used herein, the term “redispersible” is defined as a powderformulation that readily disperses and hydrates into an aqueous liquid.The polymer powders are typically produced by subjecting an aqueousdispersion of the polymer to a drying operation in which its volatilecomponents are evaporated, for example by means of spray drying orfreeze drying. The evaporation of the aqueous dispersion medium may beaccompanied by irreversible aggregation of the polymer particles of theaqueous dispersion with one another, to form secondary particles. Theformation of secondary particles results in poorer redispersibility,which is generally accompanied by poorer performance properties of thepowder. Therefore, good redispersibility in water is one of the mostimportant properties of the water-redispersible polymer powders.

DETAILED DESCRIPTION

Embodiments of the present disclosure describe the use of a rotor statormixer for producing a dispersion of starch particles in an aqueousliquid. In one or more embodiments, the starch particles of the presentdisclosure are formed from a feed starch. In one or more embodiments,the feed starch and the aqueous liquid are heated to a temperatureranging from a gelation temperature to below a solubilizationtemperature of the feed starch. At this temperature, the structure ofthe feed starch swells as it loses its crystalline structure and absorbsat least a portion of the aqueous liquid to achieve an amorphousstructure. The feed starch in its swollen state undergoes shearing toallow for the production of the starch particles of the dispersion.Dispersions of the present disclosure can have improved shelf-stability,high solid content and low viscosity, as discussed herein.

In one or more embodiments, the starch particles produced according tothe present disclosure are believed to retain the amorphous structure ofthe swollen feed starch from which they are produced. The starchparticles with their amorphous structure also can retain a discretestate in the dispersion of the present disclosure at ambient conditions,as provided herein. In contrast, it is believed that if thesolubilization temperature of the feed starch were to be achieved and/orexceeded (e.g., the starch has been “cooked” and is referred to as“cooked starch”) and sufficient water is available, the amorphousstructure of the feed starch would be destroyed to such an extent thatstarch particles having the structure and size could not be formedaccording to the processes of the present disclosure.

In one or more embodiments, the sizes of the starch particles of thepresent embodiments are orders of magnitude smaller than the feedstarch. This reduction in size greatly increases the number of starchparticles per unit volume for various uses, as discussed herein, ascompared to the use of the feed starch alone. In one or moreembodiments, even though the number of starch particles per unit volumecan result in a high solid content, as discussed herein, the viscosityof the dispersion remains surprisingly low at ambient conditions. In oneor more embodiments, it is believed that this surprisingly low viscositycan be at least partially attributed to reduced interactions between thestarch particles of the present disclosure, as compared to a situationwhere the feed starch was fully solubilized before forming thedispersion.

In one or more embodiments, the high solid content/low viscositydispersion of the present disclosure can be achieved without chemicalmodification of the starch particles. In one or more embodiments, it isalso believed that the size reduction of the starch particles may leadto enhanced stability and better properties of coatings formed fromcoating compositions that include the dispersion of the presentdisclosure. As discussed more fully herein, coating compositions thatinclude the dispersion of the present disclosure can be used inapplications such as coating compositions, adhesive compositions, and/orbinder compositions, among others as discussed herein.

In one or more embodiments, the process of the present disclosureincludes introducing the feed starch and the aqueous liquid into therotor stator mixer. The feed starch can be introduced into the rotorstator mixer as provided by the manufacturer (e.g., a dry powder, acake, and/or a slurry) and/or can be pre-wetted prior to introductioninto the rotor stator mixer. In one or more embodiments, the amount ofwater included with the feed starch, regardless of its source, iscounted as a part of the aqueous liquid in the determination of theamount of aqueous liquid in the rotor stator mixer. In one or moreembodiments, the weight of water is excluded, however, from thecalculation of the dry weight of the feed starch.

In one or more embodiments, a suitable quantity of the aqueous liquidcan be introduced with the feed starch to ensure both absorption of theaqueous liquid into the feed starch and to allow for swelling of thefeed starch and for the dispersion of the present disclosure to beformed. In addition, during the initial shearing process of the feedstarch and the aqueous liquid there is also believed to be a need tohave a sufficient solids content (e.g., feed starch) of the startingmixture to facilitate shearing of the swollen feed starch into a stabledispersion of the starch particles of the present disclosure. An exampleof this is illustrated in the Examples provided herein.

In one or more embodiments, the amount of aqueous liquid introduced withthe feed starch into the rotor stator mixer can be from 40 weightpercent (wt. %) to 55 wt. %, based on the weight of the aqueous liquidand the feed starch. All individual values and subranges from 40 wt. %to 55 wt. %, based on the weight of the aqueous liquid and the feedstarch are included herein and disclosed herein; for example, theaqueous liquid introduced with the feed starch into the rotor statormixer can be from a lower limit of 40 wt. %, 45 wt., or 50 wt. % to anupper limit of 55 wt. %, or 50 wt. % (where it is possible that thelower limit and the upper limit are both a value of 50 wt. %). Forexample, the amount of aqueous liquid introduced with the feed starchinto the rotor stator mixer can be from 40 wt. % to 55 wt. %, from 40wt. % to 50 wt. %, from 45 wt. % to 55 wt. %, from 45 wt. % to 50 wt. %,or from 50 wt. % to 55 wt. %.

In one or more embodiments, the rotor stator mixer can supply and/orremove heat to achieve and/or maintain the temperature of the feedstarch and the aqueous liquid from the gelation temperature to below thesolubilization temperature of the feed starch. For example, the rotorstator mixer can include a heating/cooling jacket that can be used tocontrol the temperature of the feed starch and the aqueous liquid in itlarge bulk phase inside the rotor stator mixer. In one or moreembodiments, heating and/or cooling can be supplied through steam and/orwater having a sufficient temperature difference with the bulk phase ofthe feed starch and the aqueous liquid to cause heating and/or coolingas desired. The action of the rotor stator may also contribute heatenergy to the feed starch and the aqueous liquid, which may have to beremoved by the heating/cooling jacket of the rotor stator mixer.

In one or more embodiments, the temperature at which the feed starch isprocessed allows for the feed starch to swell so as to achieve a propersize and hydration for shearing to the starch particles, which in turnhave a size appropriate for creating Brownian motion sufficient to keepthem suspended in the dispersion. In one or more embodiments,maintaining the feed starch and the aqueous liquid in a temperaturerange from the gelation temperature to less than the solubilizationtemperature of the feed starch causes the feed starch to lose itscrystalline structure and promotes the absorption of the aqueous liquid.As the crystalline structure is lost and the feed starch absorbs theaqueous liquid it begins to swell. The feed starch, however, does notsolubilize in the aqueous liquid (e.g., is not allowed to solubilize inthe aqueous liquid) as the temperature of the feed starch in the aqueousliquid does not achieve or exceed the solubilization temperature of thefeed starch.

As appreciated, the exact temperature ranges (e.g., from the gelationtemperature to less than the solubilization temperature) will be afunction of the feed starch selected for processing according to thepresent disclosure. By way of example, when waxy corn is used as thefeed starch the temperature can range from about 68° C. (the gelationtemperature of waxy corn at atmospheric pressure) to about 82° C. (thesolubilization temperature of waxy corn at atmospheric pressure), wherethese temperature values are given as examples with the knowledge thatthey may be different for different waxy corn grades from differentproducers and/or based on seasonal changes in the starch raw material.

It is appreciated that the gelation temperature and the solubilizationtemperature of the feed starch can also be affected by the pressure atwhich the dispersion process takes place in the rotor stator mixer.Pressure such as, for example, 101 kPa to 3447 kPa, may be applied tofacilitate processing. In other embodiments, the pressure can be from101 kPa to 1379 kPa, or from 101 kPa to 689 kPa. Such exemplary pressurecan be suitable for rotor stator mixers that operate as a continuousprocess, a semi-continuous process and/or a batch process.

In addition to swelling as it absorbs the aqueous liquid, the feedstarch in the rotor stator mixer is also exposed to a shear force ofsufficient magnitude so as to allow for the formation of the starchparticles of the dispersion. In one or more embodiments, the rotorstator mixer can impart specific mechanical energy (SME) sufficient toform the dispersion of the present disclosure. For example, the rotorstator mixer can impart SME in a range of 100 Joules per gram (J/g) ofthe components that lead to the starch dispersion to 2000 J/g during theshearing of the feed starch into starch particles. In another example,the rotor stator mixer can impart SME in a range of 100 (J/g) of thecomponents that lead to the starch dispersion to 1000 J/g during theshearing of the feed starch into starch particles.

In one or more embodiments, the SME can also have other value ranges,which may depend upon the rheology of the aqueous liquid, the feedstarch contained in the rotor stator mixer and/or the type and/orconfiguration of the rotor stator mixer used in the process. Examples ofsuch ranges can also include, but are not limited to, all individualvalues and subranges from of 100 J/g to 2000 J/g; for example, the SMEvalue can be from a lower limit of 100 J/g, 150 J/g, or 200 J/g to anupper limit of 2000 J/g, 1000 J/g, 875 J/g, or 750 J/g. For example, theSME value can be from 100 J/g to 2000 J/g, 100 J/g to 1000 J/g, from 100J/g to 875 J/g, from 150 J/g to 750 J/g or from 200 J/g to 750 J/g,among others.

In one or more embodiments, the SME provided by the rotor stator mixercan add heat to the bulk phase of the feed starch, the aqueous liquidand the starch particles present therein. Specifically, this energy canbe added in an around the shear zone of the rotor stator mixer (the areain and directly around the actual rotor stator and/or mixer structure),which can cause a local temperature increase. The residence time of thefeed starch, the aqueous liquid and the starch particles in this area,however, is very short. In addition, the feed starch, the aqueous liquidand the starch particles having been heated in the shear zone are thenalmost immediately mixed back with the large bulk phase of the aqueousliquid, which help to control the temperature in the range providedherein. This is not the case with other systems, e.g., extruders and/orjet cookers.

In one or more embodiments, geometries of the rotor and/or the statorcan be tuned to achieve a desired SME and/or shear rates for the rotorstator mixer. The operational speed (e.g., the rotations per minute) ofthe rotor may also be adjusted to create the appropriate amount of shearfor the desired particle size reduction. In one or more embodiments, itis also possible to have a stator ring that can be engaged anddisengaged relative the rotor. This allows for disengaging the statorfrom the rotor as the temperature of the feed starch, aqueous liquid andstarch particles produced during the process begins to approach, but notexceed the solubilization temperature of the feed starch. In one or moreembodiments, it is also possible to adjust a residence time values forthe feed starch in the rotor stator mixer by recirculation of theproduct through the mixing zone of the rotor stator mixer. In one ormore embodiments, the rotor stator mixer can also include bafflingand/or an independently driven distributive mixing impeller (e.g.turbine or propeller) to ensure adequate mixing and turnover within therotor stator mixer.

In one or more embodiments, shear from the rotor stator mixer breaks thefeed starch in its swollen state into the discrete units that become thestarch particles. As discussed herein, shearing the feed starch producesstarch particles having an average particle size diameter greater than 0micrometers but no larger than 2 micrometers (i.e., no larger than 2micrometers), where sizes of greater than 0 micrometers but no largerthan 1 micrometers (i.e., no larger than 1 micrometers) and/or 10 to 200nanometers are possible.

In one or more embodiments, the average particle size diameter of thestarch particles can be measured using transmission electron microscopy.Light scattering techniques are not effective for determining theaverage particle size diameter of the starch particles as the materialsappear to loosely agglomerate, giving inaccurate results. In one or moreembodiments, determining the number-weighted average particle sizediameter can be accomplished by measuring the diameter of apredetermined number of starch particles and then determining themathematical mean of the diameters of the measured particles to arriveat the number-weighted average particle size diameter.

The high solid content of the dispersion formed according to the presentdisclosure advantageously is, in various embodiments, at least 20 wt. %of the starch particles based on a total weight of the dispersion, atleast 35 wt. % of the starch particles based on a total weight of thedispersion, at least 45 wt. % of the starch particles based on a totalweight of the dispersion, or at least 48 wt. % of the starch particlesbased on a total weight of the dispersion, and advantageously is at most65 wt. % of the starch particles based on a total weight of thedispersion, or at most 55 wt. % of the starch particles based on a totalweight of the dispersion. Combinations of the upper and the lower limitsare possible. In one or more embodiments, the high solid content is from20 wt. % to 65 wt. % of the starch particles based on a total weight ofthe dispersion. In one or more embodiments, the high solid content isfrom 35 wt. % to 65 wt. % of the starch particles based on a totalweight of the dispersion. In one or more embodiments, the high solidcontent is from 45 wt. % to 55 wt. % of the starch particles based on atotal weight of the dispersion. In one or more embodiments, the highsolid content is from 48 wt. % to 55 wt. % of the starch particles basedon a total weight of the dispersion.

The dispersions of the present disclosure, in addition to having a highsolid content (e.g. the starch particles), can also have a very lowviscosity relative to conventional starch solutions at the same highsolid content. In one or more embodiments, even with a high solidcontents of the dispersion being from an upper to a lower limit asprovided herein (based on a total weight of the dispersion) thedispersion can also have a viscosity of 2000 cP or less, or 1000 cP orless as measured at ambient conditions. So, for example, with a highsolid contents of the dispersion being from 20 wt. % to 65 wt. % basedon a total weight of the dispersion the dispersion can have a viscosityof 2000 cP or less, as measured at ambient conditions. In an additionalembodiment, with a high solid contents of the dispersion being from 20wt. % to 65 wt. % based on a total weight of the dispersion thedispersion can have a viscosity of 1000 cP or less, as measured atambient conditions. In another embodiment, with a high solid contents ofthe dispersion being from 35 wt. % to 65 wt. % based on a total weightof the dispersion the dispersion can have a viscosity of 1000 cP orless, as measured at ambient conditions. In additional embodiments, theviscosity of the dispersion at the high solid content (e.g., from theupper to the lower limit as provided herein) can advantageously have aviscosity of 800 cP or less, and in various embodiments the dispersioncan advantageously have a viscosity of 600 cP or less, or even aviscosity of 400 cP or less as measured at ambient conditions. In one ormore embodiments, the dispersion of the present disclosure may also havethe high solid content provided herein with a viscosity of greater than1000 cP, or greater than 2000 cP, as measured at ambient conditions(e.g., a value of at least 10,000 cP as measured at ambient conditions).

Embodiments of the present disclosure are also able to maintain both thehigh solid content and the low viscosity at room temperature (25° C.)for various time intervals. For example, the dispersion of the presentdisclosure can maintain a viscosity of less than 10,000 cP with a highsolid content of 20 wt. % to 65 wt. % of the starch particles based onthe total weight of the dispersion after being at room temperature (25°C.) for 24 hours. In an additional example, the dispersion of thepresent disclosure can maintain a viscosity of less than 10,000 cP witha high solid content of 35 wt. % to 65 wt. % of the starch particlesbased on the total weight of the dispersion after being at roomtemperature (25° C.) for 24 hours.

In one or more embodiments, to achieve these viscosity values for thedispersion may require soluble starch present in the dispersion to bereduced from a starting molecular weight to an ending molecular weightthat is less than the starting molecular weight. In one or moreembodiments, soluble starch present in the dispersion of the starchparticles can be either produced and/or released during the heatingand/or shearing of the feed starch. In one or more embodiments, thesoluble starch includes small fragments of the feed starch, relative thestarch particles, which can significantly contribute to the viscosity ofthe dispersion. Reducing the soluble starch from the starting molecularweight to an ending molecular weight less than the starting molecularweight is helpful in reducing the viscosity of the dispersion byreducing the soluble starch into smaller fragments. Examples of suitableapproaches to reducing the soluble starch from the starting molecularweight to the ending molecular weight less than the starting molecularweight include, but are not limited to, use of chemical modificationsfor example acid or alkali hydrolysis, acid reduction, oxidativereduction, physical/mechanical degradation (e.g., via thethermomechanical energy input of the processing equipment), and/orenzymatic reduction and/or microorganisms (such as bacteria, fungi,archaea, algae, and/or protests) to reduce molecular weight the solublestarch.

In one or more embodiments, reducing the soluble starch includesenzymatically reducing the soluble starch from the starting molecularweight to an ending molecular weight less than the starting molecularweight. The use of an enzyme in the present disclosure is helpful inreducing the viscosity of the dispersion by cleaving and/orenzymatically reducing the soluble starch into smaller fragments. In oneor more embodiments, reducing/cleaving the soluble starch into thesesmaller fragments helps to improve the viscosity of the dispersion(e.g., helps to lower the viscosity) relative to not using the enzyme.

In one or more embodiments, the enzyme can be used during the process ofpreparing the dispersion of starch particles in the aqueous liquid. Inone or more embodiments, the enzyme can be a soluble and/or it can be animmobilized enzyme. In one or more embodiments, the enzyme can beincluded in the rotor stator mixer with the feed starch and the aqueousliquid, where it can act on soluble starch as it is either producedand/or released from the feed starch as it absorbs the aqueous liquid,swells and/or is sheared into the starch particles. In one or moreembodiments, the soluble starch as it is produced and/or released canhave a starting molecular weight. The enzyme enzymatically reduces thesoluble starch from the starting molecular weight to an ending molecularweight that is less than the starting molecular weight. In other words,the enzyme present in the rotor stator mixer can cleave the solublestarch into smaller fragments that have less of an impact on theviscosity of the dispersion.

In one or more embodiments, the enzyme selected for modifying theviscosity of the dispersion will depend on the compositions of the feedstarch used in forming the dispersion. Given that the feed starch isbased primarily on polysaccharide chemistries, enzymes capable ofmodifying the size (e.g., cleaving) carbohydrates will likely be mostuseful, and are known in the art. In one or more embodiments, theconcentration of an enzyme useful in the present disclosure may be farlower than would be understood and/or recommended from the art. Forexample, it is believed that useful enzyme concentrations for thepresent disclosure can be 10 to 1000 times lower than what is suggestedfor starch modification by the enzyme manufactures. This can result inenzyme concentrations in the dispersion, for example, being 0.005 weightpercent to 0.0001 weight percent relative the total weight of thedispersion (e.g. for waxy corn). As appreciated, the exact enzymeconcentration suitable for modifying the viscosity of the dispersion canbe dependent upon the temperature, the enzyme activity, the feed starchand/or the conditions under which the viscosity modification are takingplace.

In one or more embodiments, the enzyme can be used at a temperature andat a duration that is sufficient to achieve the desired viscosity forthe dispersion. In one or more embodiments, once the desired viscosityhas been achieved, the enzyme can be “deactivated.” In one or moreembodiments, the enzyme may be deactivated by removal of a componentneeded to activate the enzyme. For example, enzymes may require the useof a particular salt at a particular concentration to allow the enzymeto function. Removal of the salt would, therefore, result in thedeactivation of the enzyme. For example, the removal of calcium ions bychelation (e.g., the use of a chelating agent) may be sufficient todeactivate an enzyme that is used to cleave the soluble starch presentin the dispersion of the present disclosure.

In one or more embodiments, the feed starch can be sheared into thestarch particles of the dispersion in the absence of a cross-linker(e.g., without the use of cross linking chemistry). In one or moreembodiments, shearing the feed starch into the starch particles of thedispersion can be conducted in the absence of a surfactant. In one ormore embodiments, the use of one or more of a cross-linker and/or asurfactant is, however, possible with embodiments of the presentdisclosure. In one or more embodiments, the use of a cross-linker inpreparing the dispersion of the present disclosure may help to changethe molecular weight of the starch particle, relative not having usedthe cross-linker. Such changes to at least a portion of the molecularweight values of the starch particles of the present disclosure mayprovide for wet strength advantages derived from the dispersion in theapplication of paper coating formulations. It is appreciated that suchcross-linkers could interact with the starch particles through hydrogenbonding, covalent bonding, or a combination of both.

In one or more embodiments, a variety of rotor stator mixers may be usedaccording to the present disclosure. Examples of such rotor statormixers include, but are limited to, batch high shear mixers, inline highshear mixers, ultra high shear inline mixers, and grinding mills (e.g.,a Kady Mill), among others discussed herein. In one or more embodiments,the rotor stator mixer can be operated as part of a continuous process,a semi-continuous process and/or a batch process.

By way of example, a dispersion of starch particles in the aqueousliquid as described herein can be prepared in a continuous fashion inthe following manner. In a stirred tank, the feed starch can be added tothe aqueous liquid to create a slurry having, as provided herein, alower limit to an upper limit of the amount of aqueous liquid introducedwith the feed starch into the rotor stator mixer (e.g., from 40 wt. % to60 wt. %, based on the weight of the aqueous liquid and the feedstarch). In some cases, the rotor/stator mixer can be equipped with apowder feeding attachment which can allow the feed starch and theaqueous liquid to both be fed into the rotor/stator mixer in acontinuous fashion. The ratio of flowrates of the two streams can be setto achieve a slurry having the desired amount of aqueous liquidintroduced with the feed starch into the rotor stator mixer (e.g., from40 wt. % to 60 wt. %, based on the weight of the aqueous liquid and thefeed starch).

The slurry of the feed starch and the aqueous liquid can be pumped intoa rotor/stator mixer, such that it passes through the mixer in a singlepass. The temperature and flowrate of the slurry as well as thetemperature of the jacket of the rotor/stator mixer can be maintained sothe temperature of the slurry is from the gelation temperature to belowthe solubilization temperature of the feed starch, as discussed herein.Shear force, in ranges provided herein, can then be applied to the feedstarch in its swollen state so as to create the dispersion of starchparticles, as discussed herein. In some cases a solution of an enzyme asdiscussed herein (for example water containing 0.15 wt. % enzyme and0.19 wt. % calcium chloride) can be added continuously into dispersionin the rotor/stator mixer through a separate injection port. In somecases, a second rotor/stator mixer (equipped with a second mixer jacketfor cooling) can be placed in line after the rotor/stator mixer toprovide additional shear to further reduce the size of the starchparticles in the dispersion, if desired. Rotor speed, rotor design,rotor operational pattern(s), flowrate of the components (e.g., feedstarch and aqueous liquid), pressure and temperature are examples ofvariables in the continuous production of the dispersion of starchparticles in the aqueous liquid according to the present disclosure.Selection and values for such variables can be dependent upon, amongother things, the feed starch, the aqueous liquid and/or any optionaladditives selected in preparing the dispersion of the presentdisclosure.

In one or more embodiments, optional additives can also be used in theprocess of the present disclosure. For example, anionic and ionicstabilizers might be added to the dispersion during the shearing processto reduce particle agglomeration during drying. In an additionalexample, a plasticizer may be present in addition to the feed starch andthe aqueous liquid. Examples of plasticizers include a polyol (e.g.ethylene glycol, propylene glycol, polyglycols, glycerol, sucrose,maltose, maltodextrins, and sugar alcohols such as sorbitol), urea,sodium lactate, amino acids, or citric acid esters, at a level of from 5to 40% by weight based on the dry weight of the feed starch. However,water can already act as a plasticizer. The total amount of plasticizers(i.e. water and additional plasticizer) can range from 5% and 65% byweight based on the dry weight of the feed starch. A lubricant, such aslecithin, other phospholipids or monoglycerides, may also be present ata level of 0.5% to 2.5% by weight based on the dry weight of the feedstarch.

In one or more embodiments, optional additives can also be added to thedispersions of the present disclosure. Such additives include, but arenot limited to, biocides, anti-microbial additives, a base and/or anacid for pH adjustment, pigments, flavor or fragrance enhancers,inorganic and/or organic inert fillers or pigments, and combinationsthereof.

In one embodiment, the dispersion of the present disclosure is ready touse out of the rotor stator mixer as is. This advantageously reduces theexpense associated with drying steps required by some prior artprocesses to concentrate the material into a powder form. It is,however, possible to at least partially, i.e. less than 90 percent,substantially, i.e. at least 90 percent, and/or fully, i.e. at least 98percent, remove the aqueous liquid from the starch particles of thedispersion to concentrate the solid content of the dispersion or to forma dry redispersible powder of the starch particles for redispersionlater. As provided herein, at least partially, i.e. less than 90percent, substantially, i.e. at least 90 percent, and/or fully, i.e. atleast 98 percent, removing the aqueous liquid from the starch particlesof the dispersion can form a dry redispersible powder having an averageparticle size diameter of no larger than 20 μm, for example, no largerthan 10 μm; in the alternative, no larger than 5 μm; in the alternative,no larger than 4 μm; in the alternative, no larger than 2 μm. The dryredispersible power particles may agglomerate during the drying steps toform larger particles than the starch particles in the dispersion. Theagglomerated particles may be dispersed into a dispersion having anaverage particle size diameter of no larger than 2 μm; for example, froman average particle size diameter of no larger than 1 μm or an averageparticle size diameter of 10 to 200 nanometers.

Various means for reducing the aqueous liquid content of dispersionsand/or for drying the dispersion are known to those skilled in the art.Examples of these means include air drying, forced air drying, spraydrying, pressurized filtration and centrifugation, among others. In oneor more embodiments, the dry powder of the starch particles can befurther milled to break the particles and/or particle aggregates intothe desired size. The dry powder of the starch particles of the presentdisclosure can then be resuspended in a dispersion at a desired time. Inone or more embodiments, it may also be possible to add additional waterto the dispersion to alter the solid content to a desired level.

In one or more embodiments, dry powders of the starch particles can alsobe blended with other powders, compounds and/or dispersion prior to orat the time of resuspension. Examples of such powders, compounds and/ordispersions include, but are not limited to, latexes, latex andnon-latex binders, dispersions, pigments, among others useful for filmcoating, adhesive and/or binder systems, as are provided herein.

The starch particles of the present disclosure can also be blended withone or more of the following additional components. Such additionalcomponents can be blended with the starch particles in the dispersion orcan be blended with a dry powder of the starch particles. In one or moreembodiments, the additional component can include one or more bindercompositions such as acrylic latex, vinyl acrylic latex, styrene acryliclatex, styrene butadiene latex, vinyl acetate ethylene latex, modifiedcellulosic binders such as methylcellulose, hydroxypropyl cellulose, andcombinations thereof; optionally one or more fillers; optionally one ormore additives; optionally one or more pigments, e.g. titanium dioxide,mica, calcium carbonate, silica, zinc oxide, milled glass, aluminumtrihydrate, talc, antimony trioxide, fly ash, and clay; optionally oneor more co-solvents, e.g. glycols, glycol ether,2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, alcohols, mineralspirits, and benzoate esters; optionally one or more dispersants, e.g.aminoalcohols, and polycarboxylates; optionally one or more surfactants;optionally one or more defoamers; optionally one or more preservatives,e.g. biocides, mildewcides, fungicides, algaecides, and combinationsthereof; optionally one or more thickeners, e.g. cellulosic basedthickeners such as hydroxyethyl cellulose, hydrophobically modifiedalkali soluble emulsions (HASE thickeners such as UCAR® POLYPHOBE TR-116from The Dow Chemical Company) and hydroobically modified ethoxylatedurethane thickeners (HEUR); or optionally one or more additionalneutralizing agents, e.g. hydroxides, amines, ammonia, and carbonates.

The additional components can also include, but are not limited to,polysaccharide derivatives, including cellulose derivatives. Examples ofsuch polysaccharide derivatives include polysaccharide ethers andpolysaccharide esters, cellulose ethers and esters, and water-solublecellulose ethers. They can have one or more substituents such as of thetypes: hydroxyethyl, hydroxypropyl, hydroxybutyl, methyl, ethyl, propyl,dihydroxypropyl, carboxymethyl, sulfoethyl, hydrophobic long-chainbranched and unbranched alkyl groups, hydrophobic long-chain branchedand unbranched alkyl aryl groups or aryl alkyl groups, cationic groups,acetate, propionate, butyrate, lactate, nitrate or sulfate, of whichsome groups, such as, for example, hydroxyethyl, hydroxypropyl,hydroxybutyl, dihydroxypropyl and lactate, are capable of forminggrafts. The substituents of the polysaccharides according to the presentdisclosure are not limited to these groups. Typical polysaccharidederivatives are guar derivatives, starch derivatives, chitin or chitosanderivatives, and cellulose derivatives, but the polysaccharidederivatives according to the disclosure are not limited to these.

Examples of cellulose derivatives can include, but are not limited to,hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), ethylhydroxyethyl cellulose (EHEC), carboxymethyl cellulose, carboxymethylhydroxyethyl cellulose (CMHEC), hydroxypropyl hydroxyethyl cellulose(HPHEC), methyl cellulose (MC), methyl hydroxypropyl Cellulose (MHPC),methyl hydroxyethyl cellulose (MHEC), carboxymethyl cellulose (CMC),hydrophobically modified hydroxyethyl cellulose (hmHEC), hydrophobicallymodified hydroxypropyl cellulose (hmHPC), hydrophobically modified ethylhydroxyethyl cellulose (hmEHEC), hydrophobically modified carboxymethylhydroxyethyl cellulose (hmCMHEC), hydrophobically modified hydroxypropylhydroxyethyl cellulose (hmHPHEC), hydrophobically modified methylcellulose (hmMC), hydrophobically modified methyl hydroxypropylcellulose (hmMHPC), hydrophobically modified methyl hydroxyethylcellulose (hmMHEC), hydrophobically modified carboxymethyl methylcellulose (hmCMMC), sulfoethyl cellulose (SEC), hydroxyethyl sulfoethylcellulose (HESEC), hydroxypropyl sulfoethyl cellulose (HPSEC), methylhydroxyethyl sulfoethylcellulose (MHESEC), methyl hydroxypropylsulfoethyl cellulose (MHPSEC), hydroxyethyl hydroxypropyl sulfoethylcellulose (HEHPSEC), carboxymethyl sulfoethyl cellulose (CMSEC),hydrophobically modified sulfoethyl cellulose (hmSEC), hydrophobicallymodified hydroxyethyl sulfoethyl cellulose (hmHESEC), hydrophobicallymodified hydroxypropyl sulfoethyl cellulose (hmHPSEC) or hydrophobicallymodified hydroxyethyl hydroxypropyl sulfoethyl cellulose (hmHEHPSEC).Other suitable cellulose derivatives include cellulose ethers having athermal flocculation point in water, such as, for example, methylcellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl celluloseand hydroxypropyl cellulose.

Embodiments of the present disclosure may also employ a colorant as partof the dispersion. A variety of colors may be used. Examples includecolors such as yellow, magenta, and cyan. As a black coloring agent,carbon black, and a coloring agent toned to black using theyellow/magenta/cyan coloring agents shown below may be used. Colorants,as used herein, include dyes, pigments, and predispersions, amongothers. These colorants may be used singly, in a mixture, or as a solidsolution. In various embodiments, pigments may be provided in the formof raw pigments, treated pigments, pre-milled pigments, pigment powders,pigment presscakes, pigment masterbatches, recycled pigment, and solidor liquid pigment predispersions. As used herein, a raw pigment is apigment particle that has had no wet treatments applied to its surface,such as to deposit various coatings on the surface. Raw pigment andtreated pigment are further discussed in PCT Publication No. WO2005/095277 and U.S. Patent Application Publication No. 2006/0078485,the relevant portions of which are incorporated herein by reference. Incontrast, a treated pigment may have undergone wet treatment, such as toprovide metal oxide coatings on the particle surfaces. Examples of metaloxide coatings include alumina, silica, and zirconia. Recycled pigmentmay also be used as the starting pigment particles, where recycledpigment is pigment after wet treatment of insufficient quality to besold as coated pigment.

Exemplary colorant particles include, but are not limited to, pigmentssuch as yellow coloring agent, compounds typified by a condensed azocompound, an isoindolynone compound, an anthraquinone compound, anazometal complex methine compound, and an allylamide compound aspigments may be used. As a magenta coloring agent, a condensed azocompound, a diketopyrrolopyrrole compound, anthraquinone, a quinacridonecompound, a base dye lake compound, a naphthol compound, abenzimidazolone compound, a thioindigo compound, and a perylene compoundmay be used. As a cyan coloring agent, a copper phthalocyanine compoundand its derivative, an anthraquinone compound, a base dye lake compound,and the like may be used.

Dispersions of the present disclosure may be used, for example, indifferent coating applications such as architectural coatingapplications, automotive coating applications, paper coatingapplications, paper sizing applications, seed coating applications,conductive coatings and industrial coating applications, adhesivesapplications, binder applications, sealant applications, foamapplications, toner applications, immediate release coatingapplications, and controlled released coating applications, amongothers.

The dispersion may be employed in existing applications where starchand/or latex are used. For example, the dispersion can be used in apaper coating composition. Paper coating compositions can be preparedsubstituting wholly or partially the starch dispersion material forother conventional binders such as latex and conventional coatingstarches.

Surprisingly, a significant advantage of the dispersion of the presentdisclosure is that it can remain shelf-stable at 25° C. for a time of atleast 52 weeks.

In one or more embodiments, the dispersion of the present disclosure canbe used in a variety of applications. Such applications include, but arenot limited to, coating compositions, adhesives (e.g., tapes, labels,book bindings, etc.), pharmaceuticals (e.g., as an extender in tabletcoatings), as a binder and/or filler in wet laminations and/or woodcomposites, fiberglass shingle mats, and/or polyester spun-bondapplications like roofing and carpet backing. They could also be used inpaper coatings compositions, carpet binding applications, mastics, jointcompounds, and/or cements.

Suitable substrates for the dispersion of the present disclosureinclude, but are not limited to, cellulosic based materials, such apaper, paper board, and/or cardboard, metal based materials, polymericbased materials (synthetic and/or natural), and mineral based materials(e.g., concrete), among others. The dispersions of the presentdisclosure may also be used in existing starch applications, existingsynthetic latex applications, coating applications, latex formulationswhere some of the latex can be replaced by the dispersion of the presentdisclosure.

The dispersions according to the present invention may be applied to oneor more surface of a suitable substrate via methods known to a person ofordinary skill in the art such as spraying, printing, roll coating, jetcoating, film coating, puddle coating, curtain coating, and/or dipping,and subsequently at least a portion of aqueous liquid may be removedthereby forming a coating layer, for example a film, associated with oneor more surfaces of the substrate.

Additional subject matter included in this application includes, but isnot limited to, the following: A dispersion of starch particles preparedby the process recited herein. A binder composition comprising adispersion of starch particles prepared by the process recited herein.An adhesive composition comprising a dispersion of starch particlesprepared by the process recited herein. The coating composition asrecited herein, where the coating composition is applied to one or moresurfaces of a substrate. The coating composition as recited herein,where the coating composition is a film forming composition. The coatingcomposition as recited herein, where the portion of the aqueous liquidis removed via drying, centrifuge, freeze drying, filtration orabsorption.

EXAMPLES

The following examples are given to illustrate embodiments of thepresent disclosure and should not be construed as limiting its scope.All parts and percentages are by weight unless otherwise indicated.

Test Methods

Sheet Gloss

Sheet gloss is measured using a Technidyne T-480 instrument at anincident angle of 75°, available from Technidyne Corporation. Sheetgloss is a property that describes coated paper's shiny or lustrousappearance and is a measurement of a sheet's surface reflectivity.

Sheet Brightness (GE Brightness)

Sheet brightness is measured using a Technidyne Brightimeter Micro S-5and the Colortouch PC instrument available from Technidyne Corporation.Brightness is a numerical value of the reflectance factor of a samplewith respect to blue light. The instrument has a light source thatshines onto a piece of paper at 45 degrees with receiving optics thatview that same spot from zero degrees, perpendicular to the sample.

Brookfield Viscosity

The viscosity is measured using a Brookfield RVT viscometer (availablefrom Brookfield Engineering Laboratories, Inc., Stoughton, Mass., USA).For viscosity determination, a sample is poured into a suitably largecontainer to avoid edge effects between the wall and the spindle. Theviscosity is measured at around 25° C. with a variety of spindle sizesand rotation speeds depending on the characteristics of the sample beingmeasured. The values reported in Tables 1 and 2 were obtained with anumber 3 spindle and 100-rpm condition.

Materials

The following materials are used in the examples.

Starch A: waxy corn starch (Douglas Waxy Pearl Starch available fromPenford, Cedar Rapids, Iowa), dry powder containing about 11% moisture.

Starch B: dent corn starch (Pearl Starch available from Penford, CedarRapids, Iowa), dry powder containing about 11% moisture.

Starch C: native waxy corn starch (Merizet 300 available from Tate andLyle, Koog, Netherlands), dry powder containing about 11% moisture.

Calcium chloride: 10 weight percent solution of calcium chloride inwater (Calcium chloride from Fischer Scientific, Fair Lawn, N.J.).

Crosslinker: Glyoxal (EKA RC 5550 available from Eka Chemicals Inc.,Marietta, Ga., USA).

Insolulubilizer: Surface strength improver (Cartabond TSI (42%)available from Clariant, Muttenz, Switzerland).

Bleach: 2.5 weight percent sodium hypochlorite solution in water(household bleach available from Clorox, Corp.).

Enzyme: enzyme preparation (BAN 480L available from Novozymes A/S,Bagsvaerd, Denmark).

Chelating Agent: chelating preparation in water (VERSENOL 120 availablefrom Dow Chemical, Midland, Mich.).

Carbonate: dispersion of calcium carbonate with particle size of 90%<2μm in water (Hydrocarb® 90 available from Pluess-Stauffer, Oftringen,Switzerland), 77% solids.

Clay: dispersion of No. 1 high brightness kaolin clay with particle sizeof 90-96%<2 μm in water (Hydrafine® 90 available from KaMin PerformanceMaterials, Macon, Ga., USA), 71% solids.

Latex: carboxylated styrene-butadiene latex (CP 638NA available from TheDow Chemical Company, Midland, Mich., USA), 50% solids in water.

Caustic: 20% sodium hydroxide solution (Fisher Scientific, Fair Lawn,N.J.).

Water: De-ionized water.

Paper: An 88 gram/square meter wood-free base paper from AppletonCoated, Appleton, Wis.

Equipment

Lab Kady-Mill mixer serial number L-744 from Kady International ofScarborough, Mass. with Stator #1 mixing head and 2.24 kW motor.

GAW Agitator, model RW 60 S-VST Rotor Stator from GAW Pidlner-SteinburgGmbH, Graz, Austria. with 50 hp motor drive and a 473 liter container.

Example 1

Prepare the dispersion by first measuring an amount of Starch A anddeionized water, both at room temperature (25° C.), to make a mixturehaving a 50 weight percent solids content. Place a sufficient amount ofthe mixture into the mixing bowl of the Lab Kady-Mill mixer toadequately cover the rotor stator as to prevent splashing (e.g., where asufficient amount of the mixture for the present example is 750 grams ofStarch A and 665 grams of deionized water). Set the motor drive speedsetting of the Lab Kady-Mill mixer to number “10” (scale of 1 to 10) andmix the feed starch and water mixture having the 50 weight percentsolids content for 5.5 minutes until the resulting dispersion does notcirculate in the mixing bowl under agitation. Reduce the speed of themotor drive speed setting to number “4” and add water to the dispersionto bring the solids content to 25 weight percent. Mix the dispersion atthe motor drive speed setting number “4” for 5 additional minutes. Theresult is a stable dispersion of starch particles in the aqueous liquid,according to the present disclosure, that does not gel after storage atroom temperature (25° C.) for 24 hours.

Example 2

Prepare the dispersion by first measuring an amount of Starch A anddeionized water, both at room temperature (25° C.), to make a mixturehaving a 50 weight percent solids content. Add 1 part cross-linker basedon 100 parts of dry Starch A to the mixture. Place a sufficient amountof the mixture into the mixing bowl of the Lab Kady-Mill mixer toadequately cover the rotor stator as to prevent splashing (e.g., where asufficient amount of the mixture for the present example is 750 grams ofStarch A and 665 grams of deionized water). Set the motor drive speedsetting of the Lab Kady-Mill mixer to number “10” (scale of 1 to 10) andmix the feed starch and water mixture having the 50 weight percentsolids content for 5.5 minutes until the resulting dispersion does notcirculate in the mixing bowl under agitation. Reduce the speed of themotor drive speed setting to number “4” and add water to the dispersionto bring the solids content to 25 weight percent. Mix the dispersion atthe motor drive speed setting number “4” for 5 additional minutes. Theresult is a stable dispersion of starch particles in the aqueous liquid,according to the present disclosure, that does not gel after storage atroom temperature (25° C.) for 24 hours.

Example 3

Prepare the dispersion by first measuring an amount of Starch B anddeionized water, both at room temperature (25° C.), to make a mixturehaving a 50 weight percent solids content. Place a sufficient amount ofthe mixture into the mixing bowl of the Lab Kady-Mill mixer toadequately cover the rotor stator as to prevent splashing (e.g., where asufficient amount of the mixture for the present example is 750 grams ofStarch B and 665 grams of deionized water). Set the motor drive speedsetting of the Lab Kady-Mill mixer to number “10” (scale of 1 to 10) andmix the feed starch and water mixture having the 50 weight percentsolids content for 5.5 minutes until the resulting dispersion does notcirculate in the mixing bowl under agitation. Reduce the speed of themotor drive speed setting to number “4” and add water to the dispersionto bring the solids content to 25 weight percent. Mix the dispersion atthe motor drive speed setting number “4” for 5 additional minutes. Theresult is a stable dispersion of starch particles in the aqueous liquid,according to the present disclosure, that does not gel after storage atroom temperature (25° C.) for 24 hours.

Example 4

Prepare the dispersion by first measuring an amount of Starch B anddeionized water, both at room temperature (25° C.), to make a mixturehaving a 50 weight percent solids content. Add 1 part cross-linker basedon 100 parts of dry Starch B to the mixture. Place a sufficient amountof the mixture into the mixing bowl of the Lab Kady-Mill mixer toadequately cover the rotor stator as to prevent splashing (e.g., where asufficient amount of the mixture for the present example is 750 grams ofStarch B and 665 grams of deionized water). Set the motor drive speedsetting of the Lab Kady-Mill mixer to number “10” (scale of 1 to 10) andmix the feed starch and water mixture having the 50 weight percentsolids content for 5.5 minutes until the resulting dispersion does notcirculate in the mixing bowl under agitation. Reduce the speed of themotor drive speed setting to number “4” and add water to the dispersionto bring the solids content to 25 weight percent. Mix the dispersion atthe motor drive speed setting number “4” for 5 additional minutes. Theresult is a stable dispersion of starch particles in the aqueous liquid,according to the present disclosure, that does not gel after storage atroom temperature (25° C.) for 24 hours.

Paper Coating Compositions Prepared with the Dispersions of Examples 1Through 4

For each of the dispersions of Examples 1 through 4 prepare a papercoating composition based on 100 parts total pigment on a dry basis.Specifically, prepare a pigment slip using 60 parts by dry weight of theCarbonate and 40 parts by dry weight of the Clay, as providedhereinabove. Then add 5 parts by dry weight Latex and 9 parts by dryweight of the dispersion as provided in Table 1. Finally, add 0.1 partsby dry weight of the insolubilizer to the paper coating composition.Adjust the pH to 8.5 with 20% aqueous sodium hydroxide and adjust thesolids content with water to 61.0%.

Prepare coated paper using the paper coating compositions in thefollowing process. Utilize a laboratory bench blade coater (manufacturedby Enz Technik A G, Giswil, Switzerland) to apply the paper coatingcompositions to the paper. Set the blade metering pressure to apply 8lbs/3300 sq ft and dry the resulting paper coating composition usinginfrared and air flotation drying to reach a target moisture of 4.5%.Cut the resulting paper samples into sheets and then lab calendar usinga Beloit Wheeler Laboratory Calendar Model 753 (manufactured by BeloitManhattan, Otsego, Mich., USA) using 3 passes through a single nip at 65deg ° C. and a pressure loading equivalent to 800 pounds per linear inch(pli). The properties of the coated paper are given in Table 1.

TABLE 1 Properties of Paper coated with the Paper Coating Compositionsthat include the Dispersion of Examples 1 through 4 DispersionBrookfield GE Brightness of used Viscosity [cP] Sheet Gloss (75 deg thePaper in the Paper of Paper CMD*) of the Paper coated with the CoatingCoating coated with the Paper Paper Coating Composition CompositionCoating Composition Composition Example 1 206 67.8 86.8 Example 2 28464.0 86.9 Example 3 912 63.8 86.7 Example 4 710 65.7 86.6 *Cross MachineDirection

Example 5

Prepare the dispersion by first measuring an amount of Starch C andwater, both at room temperature (25° C.), to make a mixture having a 45weight percent solids content. Place 113.4 kg of Starch C and 126.6 kgof water in the tank of the GAW Mixer body. Set the speed setting of theGAW Mixer to 1800 rpm on the motor drive speed control and mix themixture having the 45 weight percent solids content for 30 minutes untilthe resulting dispersion reaches a temperature of 65.5° C. Add 200 partsper million based on dry weight calcium chloride via a 10% solution. Add0.00005 parts of the enzyme, based on 100 parts of dry Starch C, to thedispersion and mix for an additional 30 minutes. Reduce the speedsetting of the GAW Mixer to 600 rpm on the motor drive speed control.Add the chelating agent at 2000 parts per million and mix the dispersionfor an additional 10 minutes.

The result is a stable dispersion of starch particles in the aqueousliquid that does not gel after storage at room temperature (25° C.) for24 hours.

Comparative Example A

Prepare the dispersion by first measuring an amount of Starch B anddeionized water, both at room temperature (25° C.), to make a mixturehaving a 40 weight percent solids content. Place a sufficient amount ofthe mixture into the mixing bowl of the Lab Kady-Mill mixer toadequately cover the rotor stator as to prevent splashing (e.g., where asufficient amount of the mixture for the present example is 750 grams ofStarch B and 998.9 grams of deionized water). Set the motor drive speedsetting of the Lab Kady-Mill mixer to number “10” (scale of 1 to 10) andmix the feed starch and water mixture having the 40 weight percentsolids content for 5.5 minutes until the resulting dispersion does notcirculate in the mixing bowl under agitation. Reduce the speed of themotor drive speed setting to number “4” and add water to the dispersionto bring the solids content to 25 weight percent. Mix the dispersion atthe motor drive speed setting number “4” for 5 additional minutes.

The result is a dispersion of starch in water that gels after roomtemperature storage (25° C.) after 24 hours. The material will not pourfrom the container, and it is not suitable for a component in a coatingformulation.

Comparative Example A illustrates the need to have a higher weightpercent solids content during the shearing process (as compared to thefinal solids content of the resulting dispersion, which was in bothcases 25 weight percent solids content). In Comparative Example A therewas a 40 weight percent solids content during the shearing process, ascompared to a 50 weight percent solids content for Example 3. So, inComparative Example A there is approximately 20 percent less solidscontent, as compared to Example 3, in the mixture during the shearingprocess which allows for fewer starch particles to pass through theshearing points in the mixer. In other words, for Example 3 there isapproximately 25 percent greater solids content, as compared to theComparative Example A, in the mixture during the shearing process. Thishigher solids content during the shearing process is believed to beimportant in achieving the stable dispersion of starch particles of theappropriate average particle size diameter, as discussed herein.

Table 2, below, provides a summary of Brookfield Viscosity Values forthe Dispersions of Examples 1-5, and Comparative Example A.

Weight Percent Brookfield Solids Viscosity Brookfield Brookfield Content[cP] - Viscosity [cP] - Viscosity [cP] - Example During Shear initialafter 3 days after 10 days Example 5 45 1300 Not gelled Not gelledComparative 40 363 Not Not Example A measureable - measureable - Samplegelled Sample gelled Example 1 50 66  94  83 Example 2 50 128 120 125Example 3 50 141 683 407 Example 4 50 203 395 428

What is claimed is:
 1. A process for preparing a dispersion of starchparticles in an aqueous liquid, the process comprising: heating a feedstarch and the aqueous liquid to a temperature ranging from a gelationtemperature to less than a solubilization temperature for the feedstarch; and shearing the feed starch into starch particles having anaverage particle size diameter of no larger than 2 micrometers in theabsence of a cross-linker at the temperature ranging from the gelationtemperature to less than the solubilization temperature of the feedstarch.
 2. The process of claim 1, including crosslinking the starchparticles with a cross-linker after the shearing step.
 3. The process ofclaim 1, where shearing the feed starch into starch particles includesforming the dispersion having 20 to 65 weight percent of the starchparticles based on a total weight of the dispersion.
 4. The process ofclaim 1, where shearing the feed starch into starch particles includesusing a rotor stator to shear the feed starch into starch particles. 5.The process of claim 1, where shearing the feed starch into starchparticles is conducted in the absence of a surfactant.
 6. The process ofclaim 1, where shearing the feed starch produces soluble starch having astarting molecular weight; and reducing the soluble starch from thestarting molecular weight to an ending molecular weight less than thestarting molecular weight.
 7. The process of claim 6, where reducing thesoluble starch includes enzymatically reducing the soluble starch fromthe starting molecular weight to an ending molecular weight less thanthe starting molecular weight.
 8. The process of claim 1, where aviscosity of the dispersion having 20 to 65 weight percent of the starchparticles based on a total weight of the dispersion is less than 10,000cP after being at 25° C. for 24 hours.
 9. The process of claim 1,including at least partially removing the aqueous liquid from the starchparticles of the dispersion.
 10. The process of claim 1, including atleast partially removing the aqueous liquid from the starch particles ofthe dispersion thereby forming a dry redispersible powder.
 11. Theprocess of claim 1, including at least partially removing the aqueousliquid from the starch particles of the dispersion thereby forming a dryredispersible powder having an average particle size diameter of nolarger than 2 micrometer.
 12. A coating composition comprising adispersion of starch particles prepared by the process of claim
 1. 13.The coating composition of claim 12, where the coating composition is apaper coating composition.
 14. The coating composition of claim 12,where the coating composition is applied to one or more surfaces of asubstrate, and wherein a portion of the aqueous liquid is removedthereby forming a coating layer associated with one or more surfaces ofthe substrate.